1994 Fiscal Year Final Research Report Summary
Mechanism of aluminum injury and tolerance in plant in terms of the function of plasma membrane.
| Project/Area Number |
05660074
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Plant nutrition/Soil science
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| Research Institution | Okayama University |
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Principal Investigator |
MATSUMOTO Hideaki Res. Inst. for Bioresources, Okayama Univ., Div. of Genetics Professor, 資源生物科学研究所, 教授 (80026418)
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| Co-Investigator(Kenkyū-buntansha) |
EZAKI Bunichi Res. Inst. for Bioresources, Okayama Univ., Div. of Genetics Research Associate, 資源生物科学研究所, 助手 (90243500)
YAMAMOTO Yoko Res. Inst. for Bioresources, Okayama Univ., Div. of Genetics Associate Professor, 資源生物科学研究所, 助教授 (50166831)
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| Project Period (FY) |
1993 – 1994
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| Keywords | Higher plant / Acid soil / Aluminum stress / Response / Tolerance / Injury / Plasma membrane / Ion transport |
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| Research Abstract |
In order to characterize the mechanism of Al tolerance (Atlas 66) and Al sensitivity (Scout 66) in two cultivars of wheat (Triticum aestivum L.), the early responses to Al stress under acidic conditions were investigated. Marked inhibition of root elongation of Scout was observed upon treatment with 10muM AlCl_3 for less than 3 h. Root elongation of Atlas was only partially inhibited by the treatment with 10muM AlCl_3 for more than 6 h.Levels of Al in two portions of roots, namely, portions 0-5 mm and 5-10 mm from the tip, were lower in Atlas than those in Scout.
Both Atlas and Scout were preloaded with K^+ at pH 5.5 and transferred to distillled water at various pH values to monitor the efflux of K^+. A reduction in the pH induced increases in the efflux of K^+ in both cultivars, and the rate of efflux in Scout was twice that in Atlas at pH 4.2. AlCl_3 at concentrations as low as 5muM markedly repressed K^+ efflux at pH 4.2 and this effect was more pronounced in Scout. Ca^<2+> also had
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a repressive effect of K^+ efflux. Vanadate increased K^+ efflux, a result that suggests the involvement of a H^+ pump in K^+ efflux. These results suggest that a low extracellular pH may cause an increase in the cytoplasmic concentration of H^+ that is followed by depolarization of the plasma membrane, which may be modified by the efflux of K^+ and H^+. The characteristic defference in terms of K^+ efflux between Atlas and Scout at low pH may be caused by differences associated with plasma membrane potentials.
We compared the effect of aluminum on the calcium (^<45>Ca^<2+>) influx through putative calcium channels of plasma membrane vesicles isolated from two wheat (Triticum aestivum L.) cultivars differing in Al sensitivity. Bepridil, a calcium channel blocker, and aluminum suppressed the influx in both cultivars. However, no differences were observed in the effects of these treatments between the two cultivars.
Furtheremore, we investigated the mechanism of the inhibition of root elongation by Al from the cellular point of view. Al inhibit the cell elongation at the elongation zone specifically, where cell elongation was markedly inhibited but the cell diameter increased. Lignification in the elongation zone coincided with an inhibition of root growth of two cultivars differing in Al-sensitivity. Less
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